Gas Engineering

When natural gas escapes from gas pipework into a room its relative density will tend to make it:

• Fall, potentially causing greater concentrations at low level.

• Rise, potentially causing greater concentrations at high level.

• Prevent it from readily diffusing into the air, causing collection at the source of the escape.

• Split into its component elements producing concentrations of different gases throughout the room.

The flammability limits for natural gas (methane) are approximately:

• 2 to 10% gas in air.

• 5 to 15% gas in air.

• 10 to 20% gas in air.

• 15 to 50% gas in air.

Yellow flames seen in the radiant area of a conventional gas fire may indicate signs of:

• Lack of use.

• Flame reversal.

• The flue spigot restrictor not being fitted.

• Insufficient primary air to allow complete combustion.

A flame impinging on the walls of the combustion chamber or the surface of the heat exchanger in a gas boiler may cause:

• Vitiation causing increased combustion efficiency.

• Flame vortexing and therefore complete combustion.

• Incomplete combustion causing soot deposits to block the flueways.

• Catalytic combustion and therefore higher flame and flue gas temperature.

A blockage in the flue of a room sealed boiler is likely to result in:

• Complete combustion caused by vitiation.

• Incomplete combustion caused by vitiation.

• Complete combustion caused by reduced airflow over the burner.

• Incomplete combustion caused by excessive air passing over the burner.

What is the primary cause of carbon monoxide production in a gas boiler?

• Incomplete combustion due to insufficient oxygen.

• High humidity levels in the combustion chamber.

• Excessive air supply to the burner.

• Complete combustion of natural gas.

Which of the following is a potential consequence of a gas leak in a confined space?

• Increased oxygen levels leading to better combustion.

• Immediate dissipation of gas into the atmosphere.

• Formation of water vapor reducing humidity.

• Accumulation of gas leading to an explosion risk.

What is the effect of a blocked air intake on a gas boiler's performance?

• Higher flame temperature due to increased air pressure.

• Stable performance with no impact on combustion.

• Decreased efficiency due to incomplete combustion.

• Increased efficiency due to reduced airflow.